1. Field of the Invention
The present invention relates to a housing for a medical implant such as an implantable cardiac pacemaker, defibrillator, cardioverter, or the like.
2. Description of the Related Art
A housing for a medical implant comprises a hollow housing, which is used for receiving control electronics, capacitors, and batteries, for example. In addition, the housing comprises a terminal body, which is attached to the hollow housing and has at least one, but typically two to four electrical terminals situated in one or more externally accessible cavities of the terminal body, which are used for connecting one or more electrode lines. Such a terminal body is also referred to as a header. The hollow housing and header together result in a hermetically sealed housing which has the cited electrical components in the interior of the hollow housing, which are connected via supply lines to the electrical terminal or the electrical terminals in the header.
The hollow housing is typically manufactured from biocompatible metal. The electrical connection of the electrical components in the hollow housing to the electrical supply lines located in the header to the electrical terminals typically occurs via bushings which are introduced into a wall of the hollow housing and which terminate the hollow housing with a hermetic seal and, in addition, may also be implemented as filter bushings, which have an electrical low-pass effect.
The terminal housing or the header typically comprises transparent, insulating plastic. The electrical terminals are implemented as sockets, which may receive corresponding plugs of electrode lines. Because of the transparency of the terminal housing, whether an electrode line plug is inserted far enough into the socket of a particular electrical terminal is visible from the outside. The terminal housing may comprise a base body and/or a terminal body, which are connected to one another in a suitable way. Any other construction known from the prior art is also possible, in particular a multipart construction, in which the included components are individually assembled. Therefore, in the following only a terminal housing will be referred to.
High requirements are placed on the quality of a housing for a medical implant. In particular, the hollow housing and terminal housing must work together reliably and tightly over years. The terminal housing itself must be stable and precisely fitted over a long time.
Various approaches are known from the prior art for meeting the above-mentioned requirements. Firstly, casting the terminal housing directly on the hollow housing is known. For this purpose, the hollow housing having supply lines attached thereto for the electrical terminals and contact sockets for the electrode line plugs is inserted into a casting mold and a base body is cast around it by filling the closed casting mold with liquid plastic. The liquid plastic is permitted to cure in the casting mold and results—after removal of the casting mold—in a terminal housing produced in one work step and permanently connected directly to the hollow housing.
Alternatively, pre-mounted terminal housings are known, in which the electrical components, such as electrical contact sockets or electrical supply lines, are first inserted in prefinished injection molded parts made of plastic. Such multipart, pre-mountable terminal housings are known, for example, from WO 01/99239, EP 0 429 024, U.S. Pat. Nos. 5,282,841, or 6,205,358.